The importance of sonography in the diagnosis of septic complications following spinal surgery.

The detection of infection after surgery on the thoracic and lumbar spine is difficult due to the anatomical circumstances. Clinical symptoms, laboratory findings, and most radiological techniques are of limited diagnostic value. Among other benefits, sonography offers the advantage of early postoperative examination, even with metal implants in the operated area. In a retrospective study, 27 patients with clinically suspicious wounds were evaluated by sonography in the postoperative follow-up; all cases were verified by puncture and/or operative revision. Eleven cases turned out to be hematomas, and 16 cases were found to be infections. Accumulations of fluid, however, could not be differentiated by the established sonomorphological criteria such as internal echo structures, septation, demarcation from the environment, and reaction of the surrounding tissue. Ultrasonically guided transcutaneous needle aspiration biopsy served to differentiate the local findings and to establish the diagnosis and therefore is required as an obligatory method of investigation.